Implementation of Linear Controller for a DC-DC Forward Converter

ISSN (e): 2250 – 3005 || Volume, 06 || Issue, 04||April – 2016 ||
International Journal of Computational Engineering Research (IJCER)
www.ijceronline.com Open Access Journal Page 17
Implementation of Linear Controller for a DC-DC Forward
Converter
1
Aparna V V, 2
Dr. Nithya Venkatesan
1
M Tech Student, School of Electrical Engineering, VIT- Chennai , India-600127
2
Associate Professor, School of Electrical Engineering, VIT- Chennai , India-600127
I. Introduction
The DC to DC converters are used to get a required DC output even when the input is DC itself. That is to
change the DC voltage from one level to another. DC to DC converter has wide range of applications in power
electronics. DC to DC converters are of different types like Buck, Boost, Buck boost, Cuk, Flyback, Forward
etc. The output of all these converters will not be equal to the required when there is a change in the input. This
is because of the losses made by the passive components present in circuit. To reduce the losses there is
necessity for different controller techniques to be used.
The forward converter is the DC to DC converter which uses the transformer to increase or decrease the output
voltage depending on the transformer ratio and to offer galvanic isolation for the load. Since the output has the
multiple winding, it is achievable to supply both higher and lower voltage inputs simultaneously [1] and [2].
One important application of forward converter is used in the cars as hifi amplifiers in which they are used to
step up reasonably low battery voltage to higher voltage. Another common application of this converter is in
switch mode power supply which is found in computers and TV sets.
In this work, the hardware implementation of the forward converter is interfaced with the
MATLAB/SIMULINK and the real time controller implementation is carried out in the closed loop. The
converter is tested by means of both PI and PID controllers in simulation and in real time. The PI controller
implementation is done which is discussed in the paper by Mohammad Shahrokhi and Alireza Zomorrodi [3].
1. Proposed Forward Converter
1.1. Forward Converter Model
The circuit diagram of a forward converter which is taken up for study consists of MOSFET switches, diodes,
capacitor, inductor and a transformer for isolation. Figure 1 shows the basic circuit for the forward converter
Abstract
This paper discusses the controller implementation of a DC to DC Forward converter. The open loop
response is obtained initially. Then the closed loop control is given in real time for the Forward
converter. The MATLAB interfacing is done with the help of data acquisition card. The conventional PI
controller is used for the closed loop control and the results are analyzed under MATLAB/SIMULINK
environment.
Keywords: Data acquisition card, Closed loop, Forward Converter, Interfacing, MATLAB, Open loop,
PI Controller.

Implementation of Linear Controller for a DC-DC Forward …
The various design parameters which are considered for the study is given in Table 1.
1.2. Average State Space Model of the Proposed Forward Converter
The state space model and the average model of the forward converter are derived, when the MOSFET switch is
in ON-state position and in OFF-state position. The circuit is considered in both the conditions and the matrices
are obtained to find the state space model and thus changed to transfer function model for the ease of use [4].

II. Controller Implementation
Initially, the open loop response is made with the obtained transfer function model. Before implementing the
closed loop control in real time with PI and PID controller, the same is done in MATLAB environment.
2.1. Open Loop Response
The open loop response of the forward converter is studied by giving a step response according to the required
output. The open loop simulink diagram for the forward converter is shown in Figure 2. The output waveform of
the open loop response is given in Figure 3.
From the figure, it is observed that the output settles with the more oscillations. The peak overshoot was found
to be 9.25 V. The oscillations are found to be high in open loop response and it settles at a time of 160 s.
2.2. Closed Loop Control
The idea of using the PI and PID controller is to minimize the overshoot and to make the system to settle faster.
The simulation diagram with PI controller is shown in Figure 4. The tuning method, taken into consideration for
the closed loop control is the Zeigler-Nichols method [3] and the tuning rule for the same is specified in Table 2.
The Kp and Ki values were obtained from the open loop simulation after finding the ultimate gain and ultimate
period [6] and [7]. The values for the Kp, Ki and Kd for the proposed forward converter is given in Table 3.
Figure 5 shown the simulink diagram of a PID controller.

The set point tracking is done to the closed loop control with various set point values of 3 V and 5V so as to see
the response of the controller. The reference given for this method is from a step input which has different initial
and final values.
III. Results and discussions
The closed loop response of controllers is obtained in both simulation and real time. From each of the
simulations obtained, the maximum overshoot and settling time are found and they are compared. The output of
the closed loop with PI controller is shown in Figure 8.

It is noticed that the peak overshoot has been eliminated and the settling time is found to be 123.8 s with
oscillations. But the oscillations are sustained like in open loop simulation. For the same set point the PI
controller in closed loop is implemented in real time. The response obtained is shown in Figure 9.
From Figure 9 it is observed that the peak overshoot is 6.4 V. The settling time is found to be 8 s with
oscillations. The average output response was considered and the percentage ripple of the output is found to be
7%. Figure 10 shows the response of the PI controller for a different set point tracking. From this response, it
can be noticed that the controller responds immediately when there is a change in set point value given to the
system. Also the system finally settles to the average value of the required output within 7 s.

V. Conclusion
The different controllers were implemented for the proposed forward converter. The closed loop responses are
found for both simulation and in real time. In simulation, among the two controllers, the settling time is least
when PI controller is used in real time. It is found that the peak overshoot and the settling time were increased
when the real time implementation is done. It may be because of the charging and discharging property of the
energy storage components in the hardware kit.
References
[1] R. Erickson, New York: Chapman and Hall, 1997, “Fundamentals of Power Elecronics”.
[2] K.B. Khanchandani, M.D.Singh, “Power Electronics”, MC TataGrawhill Publishers, 2005
[3] Mohammad Shahrokhi, Alireza Zomorrodi, Department of Chemical and Petroleum Engineering, Shariff University Of
Technology,” Comparison of PID Controller Tuning Methods”.
[4] Vandana Jha, Pankaj Rai, VSRD-IJEECE, Vol.2 (8), 2012, “State Space Average Modelling Of Basic Converter Topologies “.
[5] Yeye Shen,Lie Xei, Xuiliang, IEEE Transaction 2013, “Explicit Hybrid Model Predictive Control Of The Forward DC to DC
Converter”.
[6] K.I.Hwu and Y.T. Tau. , IEEE PEDS 2005 “A Forward Converter having an FPGA-based PID Controller with Parameters On-
line Tuned”
[7] Micheal Madegon and Mark Dennis, “50 W Forward Converter With Synchronous Rectification And Secondary Side Control”.

Implementation of Linear Controller for a DC-DC Forward Converter

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (7)

Similar to Implementation of Linear Controller for a DC-DC Forward Converter

Similar to Implementation of Linear Controller for a DC-DC Forward Converter (20)

Recently uploaded

Recently uploaded (20)

Implementation of Linear Controller for a DC-DC Forward Converter